Understanding lab tests for your bird
by Bob Doneley BVSc FANZCVS (Avian Medicine) CMAV
Anyone who has taken their bird to an avian vet will almost certainly have had lab tests done on their bird, or at least been asked about having them done. Samples are collected; disappear out the back of the vet surgery, and some time later answers are provided. Sometimes the answers can tell us the problem, other times not.
But what are all these tests? What do the answers mean? I want to introduce you to the world of clinical pathology, where veterinary clinicians and pathologists become detectives, seeking an answer to that most elusive of questions - "What is wrong with this bird?"
Why do you want to do lab tests on my bird?
Although we tend to think of our birds as domesticated animals, in reality they are only one or two generations descended from their wild cousins. Compare this to dogs and cats, with hundreds of thousands of generations between them and their wild counterparts. And then look at how these dogs and cats have retained many of their natural instincts. So think how much stronger these instincts must be in birds.
The strongest instinct any animal can have is to survive. As birds are generally a fair way down the food chain, their survival instincts revolve around not getting eaten by a predator. We have all seen the TV shows where lions pull down and kill the weak, the lame and the young. This is a predator thing, and is nature's way of maintaining good genetic stock. The predators that hunt birds are no different - they prefer to take the easy prey the sick and lame.
So what do birds do? They simply try to avoid been conspicuous by not showing signs of illness. Avian vets call this the "Masking Phenomenon" and is one reason why many people think birds are soft' and are difficult to treat. A bird will not usually show any signs of illness until it is VERY sick, and can no longer mask it ie when you first notice your bird is sick, it is getting towards the end of the illness, not the beginning. Unfortunately, many people then wait a few days, to see if it gets better'. This only adds to the problem, and the result is that we are often presented with a severely ill bird, badly dehydrated and often starving after not having eaten for a few days.
Add to that, the fact that birds are very limited in how they show signs of illness they all fluff up, stop talking, have their eyes shut, stop eating, and so on. To someone with the right training and experience, there are subtle signs that can lead towards a shorter list of possible problems, but it is generally very difficult to make a definitive diagnosis based solely on a physical examination.
So what are we presented with? A critically ill patient that needs a correct diagnosis and treatment FAST if it is to be saved, but at the same time it doesn't give away many clues as to what is wrong. So in many cases we have to use lab tests to get a fast diagnosis so as to save your bird. A wait and see' approach treating the bird with something and seeing if it gets better may work in some cases, but not in others. The time lost waiting to see if your bird will respond could be the difference between life and death. So, after getting a good history from you and conducting a thorough physical examination, we will usually formulate a plan as to which tests we think will give the most information as quickly as possibly.
How accurate are these tests?
In both human and veterinary medicine, there is no such thing as a lab test that is 100% accurate, 100% of the time - no test will be always right all the time. Why?
There are a lot of variables in testing the patient, the sample, how it was collected, the test, how it was done, the skill of the person doing the test, and so on. These variables, when all put together, mean that we can never be 100% sure of the results. This applies to all tests blood tests, DNA tests, etc. Anyone who says their test is 100% accurate, or never wrong, is leading you astray. But most of the time lab results are accurate.
When interpreted carefully, and combined with a good history and a careful physical examination, lab tests can provide a lot of information about your bird's health or problem. This is why we discourage bird owners from sending samples to a lab themselves. Although it may appear cheaper and easier to do it that way, it is the interpretation of the results that is so important and unless we know what samples were taken and how they were taken, we cannot accurately interpret the results. DNA testing for disease is a perfect example of this. DNA tests are so accurate that any contamination or poor handling of the sample can give a misleading result. (This even applies to DNA sexing - contamination of a feather by another bird can give incorrect results.) Lab results ALWAYS need to be interpreted in light of the patient. (Vets have a saying treat the patient, not the lab results.)
Why didn't I get an answer after paying all that money?
Sometimes we get a lab result that doesn't appear to give us much information - on first appearances anyway. Sometimes the result is inconclusive, at other times everything comes back normal. Bird (and other animal) owners often appear to forget that a negative result is, in fact, a result. Been able to say, with a reasonable degree of accuracy, that your bird does NOT have a certain problem narrows down the list of possible problems. We need this information to arrive at a final answer to your bird's problems.
But also don't forget what I said earlier that all tests have some degree of error in their results. Sometimes a test has to be repeated because, while the answer was negative, the result does not fit in with the patient's history and signs. Once again, we treat the patient, not the test results.
What tests do you do on my bird?
There are a wide range of tests available to avian vets today. The selection of which tests to use is based on our expectations of the likely problem (based on the patient's history and physical examination), the danger to the patient of doing the test, and the cost of the test to the owner. We will always try to use the least expensive, minimally invasive tests first, which then enables us to narrow down the choice of tests before proceeding further.
Faecal tests. These are the least invasive tests. Fresh droppings are examined for parasites through faecal smears and faecal flotation tests, and bacterial/yeast intestinal infections are checked for with a Gram stain.
Cultures. If the problem is expected to be bacterial or fungal in nature (for example, if a faecal Gram stain shows abnormal bacteria), we will collect samples for a culture i.e. an attempt to grow bacteria or yeast in an incubator. They can then be identified and tested against a range of antibiotics to allow the vet to select the best drugs first time.
Blood tests. If the suspected problem is likely to be affecting any of the internal organs, blood tests can be performed to check the functioning of these organs. This is done by measuring the levels of certain chemicals in the blood, which will either increase or decrease with damage to particular organs. As well as these tests (biochemistries, as they are known), we will also want to know what the patient's white cell count is (as a measure of how the bird is trying to fight the problem), and whether it is anaemic or dehydrated. This is done by a CBC a complete blood count.
X-rays. These are taken to look at the relative size and positioning of internal organs and bony structures, and also to look for foreign bodies such as pieces of metal in the stomach. This can give a lot of information about a patient that may not be obtainable elsewhere.
Biopsies. Although blood tests can tell us which organs are been affected, they often cannot tell us exactly what sort of problem is occurring. Without that knowledge, veterinary treatment can be only supportive at best. To determine exactly what the problem is, it is often necessary to surgically biopsy the affected organ, i.e. remove a small piece and send it to a lab for microscopic analysis. We then know exactly what is happening, and we can give more exact treatment.
Autopsies. In a flock situation, the fastest and most accurate way to obtain a diagnosis is to autopsy a recently dead bird. If you are losing birds, make sure you take a fresh body or a dying bird to your vet and request an autopsy. We will perform an autopsy, but sometimes it is necessary to send tissue samples to a lab to get a final answer.
Special tests. In addition to the tests above, there are other, more specialised, tests. These include blood or faecal tests for psittacosis, DNA tests for viral diseases, blood and feather tests for Beak and Feather Disease, and so on. These tests are usually selected after either ruling out other problems through using the tests described earlier, or if we think there is a special need to do the test.
Are there any risks to my bird?
The more invasive a test is, the higher the risk to the patient. This is why we will rarely, for example, biopsy a liver or kidney until other tests have indicated a problem with those organs. Having said that, biopsies performed by an experienced avian vet are usually no more dangerous than other minor surgical procedures.
But in very sick birds, even collecting a blood sample can be dangerous. For example a bird with severe liver disease may be unable to clot its blood. Even collecting a small sample of blood can see the patient bleed to death. These types of accidents are unpredictable, but fortunately very rare.
Lab tests are an essential tool in determining your bird's health status. But you need to remember that the more limitations you place on testing, the slower it will be to find an answer. Because birds instinctively hide signs of illness and have such limited ways of displaying it, these tests are usually necessary to find out what is happening, which then enables us to more quickly and more accurately treat your bird.
We will discuss with you what tests are appropriate for your bird, and the likely costs of such testing. Do not be afraid to ask for more information about these tests, especially the likely benefits compared to the expected costs and possible risks. By working with us, we can both do the very best for your bird.